66681728 has 32 divisors (see below), whose sum is σ = 133238520. Its totient is φ = 33241600.

The previous prime is 66681677. The next prime is 66681739. The reversal of 66681728 is 82718666.

It is a tau number, because it is divible by the number of its divisors (32).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 62318 + ... + 63378.

Almost surely, 2^66681728 is an apocalyptic number.

It is an amenable number.

66681728 is a deficient number, since it is larger than the sum of its proper divisors (66556792).

66681728 is a wasteful number, since it uses less digits than its factorization.

66681728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1566 (or 1554 counting only the distinct ones).

The product of its digits is 193536, while the sum is 44.

The square root of 66681728 is about 8165.8880717286. Note that the first 3 decimals coincide. The cubic root of 66681728 is about 405.5106660962.

The spelling of 66681728 in words is "sixty-six million, six hundred eighty-one thousand, seven hundred twenty-eight".